We are moving to disable student to student chat. Unfortunately, that also will disable Teacher to Student chat. A replacement for that is to use private channels.

Some notes:

Here is the quick step version of how to do that. You will need to create a private channel for every student or group of students that you want to chat with. You could create one for each student OR if it doesn't need to be private you could create one for each team.
Starting the message with "@" and their name will alert them that they have a new message.
There can be as many people as you want in a private channel. So, you could create a private channel with you and a fellow teacher or tutor to allow multiple people to chat with the student.

Here's a quick video showing me creating a private channel for our fake student "testing.testing". "testing" is in my robotics team and I create a private channel for him, send him a message, and he replies.
(NOTE: there is no audio)

Create the channel

Create a team with the students you need to chat to. (or go to one you've already got setup).
click the triple dots to the right of the team name,
click "add channel"
give the channel a name like whatever student name you want.
click the dropdown under "privacy" and select private.
click "next"
find and add the student(s) that you want in the channel *you can also add multiple teachers. So you could have several flex faculty in the channel if you wanted
click "add" then done

Use the channel as a chat replacement:

go to the team
click on the channel
click "new conversation"
type you message and hit enter.
HOWEVER, if you want them to be alerted that you are typing, you can start your message with @ and then start typing their name this will mention them in the comment and alert them that they were mentioned.
If they @ you, then it will work very much like chat.

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